Pneumatic drive system for thread cutting devices for sewing machine



United States Patent [72] Inventor Nerino Marforio Milan, Italy [21 Appl. No. 784,435

[22] Filed Dec. 17, 1968 [45} Patented Nov. 24, 1970 [73] Assignee S.P.A. Virginio Rimoldi and Company Milan, Italy an Italian corporation.

[32] Priority Jan. 16, 1968 [3 3 1 Italy [54] PNEUMATIC DRIVE SYSTEM FOR THREAD CUTTING DEVICES FOR SEWING MACHINE 6 Claims, 5 Drawing Figs.

[52] U.S.Cl. 112/219, 112/252,112/239 [51] Int. Cl D05b 69/24 112/219,

[50] Field of Search 2l9A,2l9FO, 252, 220

[56] References Cited UNITED STATES PATENTS 1,962.905 6/1934 Miller 3,250,237 5/1966 Myska 112/252 3,253,561 5/1966 Block ....1l2/219(A)UX 3,347,194 10/1967 Hale et al.. .l.12/2l9(FO)UX 3,359,933 12/1967 Bono 112/252 3,400,677 9/1968 Bowers et al. ..l12-/2l9(A)UX Primary Examiner-H. Hampton Hunter Attorney Finnegan, Henderson & Farabow ABSTRACT: A pneumatic drive system for thread cutting devices of a sewing machine is provided with a pneumatic drive device which is mechanically connected to a sewing machine power source. The pneumatic drive device is connected to a pneumatic supply line and to a sensing device for determining whether the sewing needle of the machine is in its uppermost position. The pneumatic drive device is also connected to an auxiliary pneumatic container which, in turn, is connected to a distributing valve. The auxiliary container receives a sufficient amount of compressed fluid to cause the distributing valve to be operated once after each stitching operation of the sewing machine to operate the thread cutting devices. The auxiliary container is supplied with compressed fluid while the sewing machine is running and provides compressed air to the distributing valve when the sewing machine is stopped with its needle located in its uppermost position.

Patented Nov. 24, 1970 Sheet INVENTOR INERINOIMARFORIO W BY m ATTORNEY PNEUMATIC DRIVE SYSTEM FOR THREAD CUTTING DEVICES-FOR'SEWING MACHINE The present inventionrelates to a pneumatic drive system for thread cutting devices of a sewing machine and, more par-' with its own needle selectively positioned in lowermost or uppermost position, said means comprising a driving electric motor and a clutch operating arm for coupling operatively said machine with the motor.

In the machines of the above-mentioned type there is the fault causing said thread cutting device to be operated when either said machine is not yet stopped or said needle is not in its proper own uppermost position, whereby, frequently it may occur that the cutters, during their work strokes, interfere with the needle, breaking the latter or damaging themselves.

Further, in said machines there is the inconvenience due to the possibility of reoperating the thread cutting devices without executing intermediate stitches with consequent slipping of the threads out from thread gripping means and of unthreading oi the stitch forming members by restarting the sewing operations.

The purpose of the present invention is to overcome the above-mentioned inconveniences through the elimination of said faults,

Therefore the technical problem to be solved is to provide a pneumatic drive system for thread cutting devices having a safety device to prevent the premature thread cutting operation and to prevent therepeating of said operation if it is not intercalated by the execution of some stitches and this to avoid damage either to the machineor to cutters.

According to the invention, for solving said technical problem a system is provided, wherein a pneumatic drive device which is mechanically connected to the clutch operating arm of an electric motor, is connected on one hand to a pneumatic supply line andon the other to acontrol device for controlling the needle positioning and to an auxiliary pneu matic container in its turn connected to a spring rcturnair cylinder by a distributing valve caused to be operated by the control device; the pneumatic drive device being provided to charge the auxiliary container with compressed air when machine is running and to cause the control device to be operated when machine is stopped with its own needle in the uppermost position; the control device being, provided to operate the distributing valve in order to permit the compressed air contained in the auxiliary pneumatic container to be admitted into the spring return air cylinder; the auxiliary pneumatic container being provided to receive a sufficient amount of compressed airfor operating the spring return air cylinder once for each stitching operation because said spring return air cylinder is provided to operate thread cutting devices ofthe machine,

The main advantage of the present pneumatic drive system lies in the provision of one single thread cutting operation for each stitching operation in order to assure the correct stitching execution restarting of sewing machine. Another advantage reached by the present pneumatic drive systemlies in the elimination of any electric element from the drive system for thread cutting device, which is composed entirely by pneumatic elements. From this derives the possibility to provide the sewing machine with electric motor of any type, on condition that said motor is equipped with the needle positioning means; therefore electric circuits of said means do not need these transformations which are otherwise requested by the thread cutting devices for operating them, because the working sequence ofsaid thread cutting devices is entirely different from that of the needle'positioning means.

Other aims and advantages of the present invention are those which are inherent and which will become apparent from the following detailed description ofa preferred embodimeat of realization 'whichdescription is referred to the accompanying drawings, wherein HO. 1 shows diagrainmatieally-the system according to this invention;

H0. 2 shows an enlarged sectional view of pneumatic drive device;

FIG. 3 shows the balance wheel of the sewing machine to which the control device for needle positioning can connect; and v FlGS. 4-5 show an enlarged sectional view of said control device.

In FIG. I is diagrammatically shown a sewing machine 10 having a thread cutting device, not evident in the enclosed drawings, which is equipped with device for cutting and gripping the needle and the looper threads at the end of the stitching operation, after the needle has been automatically positioned in its own uppermost position in correspondence to the top dead center. I

The sewing machine 10 is caused to be driven by an electric motor 11 equipped with the usual means for performing the selective needle positioning. The electric motor 11 comprises a clutch means of which is evident outwardly a clutch operating arm 12 which is provided to couple the rotor of said motor with a driving pulley 13 in order to cause the sewing machine 10 to be driven by common driving belt 14 and a driven pulley 15. A conventional electriccircuit (not shown) is provided for controlling the operation of electric motor 11. The electric circuit operates in conjunction with clutch operating arm 12. The circuit is designed to stop the needleof the sewing machine in either its uppermostor lowermost position. The connection between the driving pulley l3 and the rotor is determined by moving in a downward direction the clutch operating arm 12 by its own manual control which may be provided in the form of, for example, a common treadle 16.

The mechanical connection between the clutch operating arm 12 and the manual controlcomprises a first rod 17 the lower end of' which is hinged .to the fore part 18 of the treadle and the upper end of which is slideable freely upwards mounted within a bracket 19 on which isiixed a second rod 20.

In the upper end, the rod 17 is provided with a pair of nuts 21 adapted for avoiding the slipping of said rod 17 out of the bracket 19 when the treadle 16 is depressed.

On said bracket 19 is mounted a three-way hand-operated valve 22 ofa pneumatic drive device 23.

The three-way hand-operated valve 22 comprises a cylinder within is slidably mounted a spring pressed piston 24 formed with a rod 25 projecting down from the cylinder which is placed against an adjustable collar 26 of the first rod 17.

Mounted within said cylinder is a return spring 27 provided to maintain the piston 24 in its own rest position in correspondence to which a conduit 28, connected to a pneumatic supply line 29, is connected to a conduit 30 of a normally closed valve 31 of the pneumatic drive device 23. Said valve 31'comprises a cylinder fixed on the upper end of the second rod 20 and within which there is a slideable spring pressed piston 32 equipped with a rod hinged on the clutch operating arm 12 of the motor 11. Between the piston 32 and the upper wall of the cylinder of said valve 31 is mounted a return spring'33 the strength of which is slightly greater than the return spring, not shown, of said clutch operating arm 12. This isprovided for pulling down said lever 12 just before the spring pressed piston 32 moves within the cylinder of normally closed valve 31. Further, the return spring 33 is provided for maintainingsaid piston 32 in its own rest position in correspondence to which the port-of the conduit 30 connecting the three-way handoperated valve 22 to the normally closed valve'31, is closed in such a way that an air passage through the conduit 34 is not possible.

From the conduit 30 extends a conduit 35 which is connected to a needle position sensing device 36. Compressed air is supplied from pneumatic supply line 29 through the threeway hand-operated valve 22 and the conduits 30 and 35 into needle position sensing device 36 wherein the compressed air maintains a piston 41 in its rest position. From the pneumatic supply line 29 extends another conduit 37 through which compressed air is supplied to a distributing valve 38 which is directly connected by conduits 39 and 40 to the thread cutting devices of the sewing machine.

, When twin pistons 42 of distributing valve 38 are in the position illustrated in FIG. 1. the compressed air which is admitted into the distributing valve flows into conduit 39.

From the conduit 39, lastly. the compressed air flows through the thread cutting devices in such a manner to maintain them in a safety or rest position. The disposition of twinpistons 42 is due to an action of a spring 43 urging a piston 44 of a spring return air cylinder 45 connected to said twinpistons 42 by a rod.

Depressing the fore part 18 of the treadle 16. the clutch operating arm 12 is also depressed and the sewing machine is caused to be started. Continuing said depression on treadle 16 the clutch operating arm 12 having arrived at the end of its stroke and the strength of the return spring 33 is overcome, thereby the cylinder of the normally closed valve 31 is moved in respect of the spring pressed piston which connects the conduits 30 and 34 together.

In consequence of this, the compressed air is free to charge the auxiliary container 47 flowing from the pneumatic supply line 29 through the conduit 28, the three-way hand-operated valve 22 and the conduits 30 and 34.

The auxiliary container 47 is provided to receive a sufficient amount of compressed air for causing once only the piston 44 of the spring return air cylinder 45 to he slid in contrast tothe action of the spring 43, the auxiliary container being con nected to said cylinder 45 by a conduit 48. a distributing valve 49 of control device 36 and by a conduit 50. At the end ofthe stitching operation. the treadle 16 is released and the same returns to its own rest position in consequence of the combined action of said return spring of the clutch operating arm 12 and of said return spring 33 of the normally closed valve 31.

As consequence of this. the spring pressed piston 32 returns in its own rest position-and closed both the accesses of the conduit '34 and the auxiliary container 47 which is charged of compressed air. a

1n the meantime the machine 10 is stopped with the needle positioned in its own lowermost position (such positioning has been caused automatically by the suitable electric circuit above-cited).

in these conditions the machine can be restarted or alternatively the thread cutting devices can be operated for cutting as described above.

In the case in which the thread cutting devices are operated,

the operation is obtained moving the treadle 16 in areverse direction, namely depressing the back part 51 of the treadle 16 to which correspond mainly both the reversing of the needle position by the operating of a suitable control of the elec tric circuit, not shown, combined with said clutch operating arm 12. and the raising of the fore part 18 and the first rod 17 which slides freely within the bracket 19 which does not move because it is fixed to clutch operating arm 12 through rod and valve 31 which cannot move upwards from the rest positions. The sliding of the first rod 17 moves the adjustable collar 26 against the push rod which is slid jointly to the spring pressed piston 24 in contrast with the action of return spring 27. Said piston. thereby. closesthe compressed air passage from the conduit 28 to the conduit and simultaneously opens the compressed air passage from the conduit 28 to a conduit 52 connecting the three-way hand-operated valve to the control device 36 and admitting the compressed air on the opposite part of the piston 41. In consequence of this. the piston 41 is pushed towards the right whilst the conduit discharges to atmosphere the compressed air contained in the cylinder through an exhaust opening formed in valve 22 which is explained below in more detail in the description of the em bodiment of the pneumatic drive device shown in FIG. 2. In order to permit the operating of the thread cutting devices only when the needle is stopped in its own uppermost position. a balance wheel 53 which is formed with a slot 54, is keyed on the main shaft 55 of the sewing machine 10 (see also HO. 3). Said slot 54. which is of a particular angular extension. is in relationship with the sewing machine needle in such a way as to be situated across path of a push rod 56 of the control device 36 (see also FIGS. 4 and 5) when said needle is positioned in correspondence of its own top dead center. The push rod 56 is formed with a resilient rod mounted on a pin 57 supported by a plate 58 fixed to a rod 59 of the piston 41. When the piston 41 is pushed to the right by the compressed air flowing from the conduit 52. the push rod 56 reach the balance wheel 53, and engages the slot 54 if the latter is positioned across push rod path. In this case. the piston 41 accomplishes entirely its stroke. 1f needle is not positioned exactly in correspondence to said top dead center. the slot 54 is not disposed across said path in front of the push rod 56 which, thereby, arrives against the balance wheel body, preventing the piston 41 from accomplishing entirely its rightward stroke. The angular extension of the slot 54 has such a valve which allows a needed positioning error of t l millimeter. (0.03937 in.).

Since the piston 41 is connected to a piston 60 slidably mounted within the distributing valve 49. the compressed air passage from the conduit 48 to the conduit 50 depends on the distance of the stroke accomplished to right by said piston 41. For this reason, said passage is only possible when needle is exactly positioned in its own uppermost position and, vice versa. said passage is not possible when the rod arrives against the balance wheel body to which corresponds the incorrect needle positioning. When the piston 41 has entirely accomplished its rightward stroke. an air passageway has been open from conduit 48 to conduit 50 as a consequence of the rightward movement of the piston 60 connected to piston 41. The compressed air contained in the auxiliary container 47 flows into the spring return air cylinder 45 and pushes the piston 44 in opposition to the action'of spring 43 to a position at which an exhaust opening (not illustrated) is opened. The compressed air discharges through the exhaust opening to the atmosphere. The piston 44 slides and moves the twin-piston 42 of the distributing valve 38, connecting the conduit 37 to the conduit 40, and so reversing the action of the compressed air on the thread cutting devices which perform the first phase of their work cycle. As soon as the compressed air contained in the auxiliary container 47 is entirely exhausted, the spring 43 presses against the piston 44 which returns twin-pistons 42 to their rest position, restoring the compressed air passage from conduit 37 to conduit 39 to which corresponds to the second phase of the work cycle of said thread cutting devices. that is. cutting and gripping of needle and looper threads. All these operations are simultaneous in consequence of the action performed on the treadle 16 which therefore can immediately be released. By releasing the treadle, the return spring 27 presses the piston 24 to its rest position, interrupting the compressed air passage to conduit 52 and restoring the compressed air passage to conduit 30. The compressed air contained in the conduit 52 discharges immediately to the atmosphere through the exhaust opening formed in valve 22 and the piston 41 can be moved to its rest position, disengaging the push rod 56 from the balance wheel slot 54. A restoration of the thread cutting operation is no longer possible because the auxiliary container 47 is now completely discharged. It is not possible to recharge said auxiliary container before reopening removing the normally closed valve-31. But to this operation also corresponds the coupling of the sewing machine with the motor, thereby the work starting occurs always with the needle and looper threads gripped by the thread cutting devices, and. therefore, the cutting operation of said threads is possible after the formation of some stitches. The rightwards stroke of piston 41 and push rod 56 are delayed in respect of the needle positioning by a throttle valve 61 provided on the conduit 52. Said throttle valve is provided for admitting the compressed air slowly into the cylinder of the control device 36 so that the entire rightward movement ofpiston 41, namely the engagement of the slot 54 by the push rod 56, is accomplished after needle positioning when the sewing machine is stopped.

Another unfavourable condition in addition to the incorrect needle positioning is determined by the raised position of the sewing machine presser foot. For this reason a pressor foot lifter device has been provided to be inserted ahead of the intake duct of the pneumatic supply line and which is constituted by a three-way manually controlled tapped valve 62 operated by a suitable control constituted, for examplerby a knee-operated control device 63.

Said three-way tapped valve, which is constantly maintained in a rest position by a suitable spring 64, provides the compressed air passage from intake duct to the pneumatic supply line 29 by twin-pistons 66 appropriately positioned. When the knee-operated control device 63 is moved in the direction of the arrow A, said pistons 66 are pushed to the right and in such a way the compressed air passage to the pneumatic supply line 29 is interrupted, rendering inactive that portion of the pneumatic control device which is connected to the pneumatic drive device 23. At the same time the pneumatic air passage is admitted into a conduit 67 which is connected to a piston 69 suitably connected to the presser foot 70 of the sewing machine 10. The compressed air which is in such a way admitted into the spring return air valve determines the sliding of the piston 69, in opposition to the action of a suitable spring 71, and consequently determines the raising of said presser foot 70. At the end of the manual action on the knee-operated control 63, the spring 64 pushes the piston 66 in its own rest position, bringing again said portion ofpneumatic drive device in condition to operate again.

A modified embodiment of the pneumatic drive device 23 (see FIG. 2) consists of a normally closed valve 31 for charging with compressed air the auxiliary pneumatic container 47 and of the three-way hand-operated valve 22 for operating the control device for controlling the needle position, both incorporated in a single cylindrical support 72. Within said support are mounted two resilient slidable threaded rods 73 and 74, the end of which project outwards from said cylindrical sup port. The rod 73 of the normally-closed valve 31 is connected to the clutch operating arm 12 of the electric motor 11 and the same is pushed towards the inside of the support 72. by a return spring 75 pressing with one of its ends against the wall 76 of the support 72 and with the other end against an annular abutment 77 with which the rod is equipped and which is provided as stroke stop. Said rod is also provided with a shank 78, which is equipped with a portion 79 having a diameter lightly smaller than said shank and provided for connecting a conduit 80 to a conduit 81 with-which the support 72 is provided.

The conduit 80 is connected to the auxiliary pneumatic container 47 whilst the conduit 81 is connected to the pneumatic supply line 29. in their rest position, the two conduits are not connecting with each other. In the shank 78 is provided an axial hole 82 ending at the outside of the portion 79 by a radial hole 83. The rod 74 of the three-way manually operated valve can be connected to the treadle 16, likewise to the first rod 17, and is urged usually towards the outside of the support 72 by a return spring 84 pressing with one end against an intermediate wall 85 of said support and with the other end against an annular abutment 86 of the rod. which is provided to prevent the rod 74 slipping out ofthe support 72. Said rod is formed with a shank 87 inside of the support 72, and said shank is provided with three intermediate portions 88, 89 and 90 having a smaller diameter. The portion 88 is provided'for discharging to atmosphere, through an outlet port 91, the compressed air containedin the conduit 92 connected to the control device 36 likewise to the conduit 35 of FIG. 1. The portion 89, which is provided with a radial hole 93 in connection with an axial hole 94 which is in its turn connecting to the axial hole 82 of the rod 73, is provided to admit the compressed air flowing from the conduit 81, alternatively into the conduit 92 or into a conduit 95 connected to a control device 36 likewise to the conduit 52 of FIG. 1. Finally the portion 90 is provided to connect toatmosphere, through an outlet port 96, the conduit 95 when the rod 74 is in its rest position. As for the pneumatic drive device 23 of FIG. 2, depressing the fore part of the treadle 16 the clutch operating arm 12 is also depressed, so that,

continuing said action, the rod 74 and the support 72 are pulled down, as a single piece, whilst the rod 73 is stopped. The shifting movement of the support 72 in respect of the rod 73 causes the compression of the spring 75 and the disposition of the portion 79 in front of conduits 80 and 81 which in such a way are in communication between themselves. The compressed air flows freely from the conduit 81 to the conduit 80 and from the latter to the pneumatic auxiliary container 47. When the treadle 16 is released, this corresponding to stopping of the sewing machine, the spring 75 extends, bringing the rod 73 into its rest position again, interrupting once more the compressed air passage from the conduit 81 to the conduit 80. Now' depressing the back part of treadle, the rod 74 is urged upwards in contrast to the action otthe spring 84, whilst the support 72 stops, because the annular abutment 77 of the rod 73 prevents'it moving The relative shifting between the support 72 and the rod 74 caused the disposition'of the portion 88 in front of the conduit 92. lnthis case, the compressed air contained in said conduit, admitted through the conduit 81 and the holes 83, 82, 94 and 93 and provided for maintaining the control device 36 in its rest position, discharges to atmosphere through the outlet port 91. At the same time, the portion 89 is disposed in front ofthe conduit 95 which thus is connected to the conduit 81 for admission of the compressed air. Said air is admitted into the control device cylinder on the opposite part of the piston 41 which is therefore pushed rightwards and moves the push rod 56. The moving of the portion is disregarded, not leading now to any particular action. When the depression ofthe treadle is ended, thespring 84 extends bringing the rod 74 in its rest position again. As consequence of this, the portion 88 moves from the conduit 92 closing the air passage to atmosphere; the portion 89 disposes again in front ofthe conduit 92 which receives the compressed air and thus causes the return of the push rod 56 to its rest position, lastly the portion 90 disposes in front of the conduit connecting the same to the outlet port 96 through which the air contained in the conduit 95 discharges to atmosphere permitting the said return ofthe push rod 56.

lclaim:

1. in a pneumatic drive system for controlling the operation of a fluid-operated thread cutting device of a sewing machine having a sewing needle driven between uppermost and lowermost positions by a motor connected to the sewing machine through a clutch provided with a clutch operating arm movable from operative to inoperative positions:

a first fluid-operated cylinder for controlling the operation ofthe thread cutting device;

a fluid-operated needle position sensing device for determining wh'ether the sewing needle is in its uppermost position;

an auxiliary fluid container;

a treadle normally positioned in an intermediate inoperative position and being selectively movable in a first direction from the intermediate inoperative position to a first operating position and in a second direction from the intermediate inoperative position to a second operating position;

a pneumatic drive device connecting the clutch operating arm to said treadle for moving the clutch operating arm to its operative position when said treadle is moved to its first operating position and for returning the clutch operating arm to its inoperative position when said treadleis moved to its second operating position;

said pneumatic drive device including a first fluid contro valve connected to said auxiliary fluid container and operated by movement of said treadle to its first operating position for supplying pressurized fluid to said auxiliary fluid container;

said pneumatic drive device also including a second fluid control valve connected to said needle position sensing device and operated by movement of said treadle to its second operating position for supplying pressurized fluid to said needle position sensing device to operate said sensing device to determine whether the sewing needle is in its uppermost position; and

means connecting said auxiliary fluid container to said first fluid-operated cylinder and operated by said needle posi tion sensing device for supplying pressurized fluid from said auxiliary fluid container to said first fluid-operated cylinder only when said needle position sensing device determines that the needle is in its uppermost position to operate the thread cutting device.

2. In the pneumatic drive system of claim I, wherein said pneumatic drive device includes a support. a first rod connecting said support to said first fluid control valve for opening said first fluid control valve when said'treadle is moved to its first operating position and for closing said first fluid control valve when said treadle is moved to its second operating position, and a second rod connected to said treadle and slidably connected to said support for engaging said support when said treadle is moved to its first operating position to move the clutch operating arm to its operative position and for moving relative to said support when said treadle is moved to its second operating position.

3. In the pneumatic drive system of claim 2 means connected to said second rod for operating said second fluid control valve when said trea dle is moved to the second operating position.

4. In the pneumatic drive system of claim 1, wherein the needle position sensing device comprises:

a second fluid-operated cylinder connected to said second fluid control valve having a piston slidably disposed therein and a push rod projecting from said cylinder and movable with said piston; and

a wheel rotatably mounted adjacent to said second fluidoperated cylinder and driven by the sewing machine motor, said wheel having a slot formed therein for receiving said push rod, said slot being in alignment with said push rod when the needle of the sewing machine is in its uppermost position.

5. In the pneumatic drive system of claim 4 wherein said means connecting said auxiliary fluid container to said first fluid-operated cylinder includes a distributing valve. said distributing valve having a piston slidably mounted therein and connected to said piston of said second fluid-operated cylinder for closing said distributing valve when said push rod is in a retracted position relative to said wheel and for opening said distributing valve when said push rod is advanced into said slot formed in said wheel.

6 In the pneumatic drive system of claim 1. wherein the pneumatic drive device comprises:

a housing for supporting said first and second fluid control valves therein;

a first rod slidably mounted at one end of said housing and connecting said first fluid control valve to the clutch operating arm for operating said first fluid control valve when said treadle is moved to its first operating position; and

a second rod slidably mounted at the opposite end of said housing and connecting said second fluid control valve to said treadle for operating said second fluid control valve when said treadle is moved to its second operating position. 

